1. Field of the Invention
The present invention generally relates to an installation structure for installing a lead advancing mechanism for advancing a lead by a predetermined amount, in an outer cylinder of a writing instrument (e.g., a mechanical pencil).
2. Description of the Related Art
A conventional writing instrument has been disclosed in, for example, Published Unexamined Utility Model Application No. 61-37990 or Published Unexamined Utility Model Application No. 61-40284.
In a writing instrument (e.g., mechanical pencil) disclosed in these Publications, a lead advancing mechanism housed in an outer cylinder has a lead pipe, a chick fixed at the front end of the lead pipe, a chuck ring fitted outside a head of the check to tighten the head of the chuck, a stopper abutting the read end of the chuck ring, and a chuck spring inserted between the front end of the lead pipe and the front end portion of the stopper to normally urge the chuck to the rear in the axial direction via the lead pipe. A stopper fixing hole is formed in the peripheral surface of the outer cylinder. By fixing a stopper protrusion of the stopper of the lead advancing mechanism in the stopper fixing hole, the lead advancing mechanism is installed in the outer cylinder without decoupling from (e.g., coming off) the outer cylinder.
However, in the installation of such a conventional lead advancing mechanism, the stopper fixing hole must be formed in the outer peripheral surface of the outer cylinder, and is visible from the outside, Thus, the writing instrument's appearance is poor. Therefore, another part must be provided on the outer peripheral surface of the outer cylinder to make the stopper fixing hole invisible from the outside.
Also, in assembly, the stopper protrusion must be brought to the stopper fixing hole by moving the lead advancing mechanism including the stopper in the outer cylinder. When the stopper protrusion protruding in the outward direction is moved in the outer cylinder, a large resistance is exerted by the inner peripheral surface of the outer cylinder, so that the operation is slow, or the inner peripheral surface of the outer cylinder may be damaged.